Froth flotation of nonmetallic ores with black liquor soap in acid circuit



UNITED STATES PATENT orrica morn non-non or Nomnmimc onus gr BLACKLIQUOR soar in ACID cm-- Elmer William can, our Greenwich, assignor toAmerican Cylnamld York, N. Y.,- a corporation of Maine No Drawing.Application Se'ptember 22, 1945,

sfllal No. 818,052

1 2Claims. (01.209-166) 2 This invention relates to the beneflciation byagent cost." Also, because it gives a very poor froth flotation of themineral values of various quality of froth it does not readily lenditself to ores. In particular, it relates to a novel reagent cleaningoperations and when used on phosphate combination suitable foruseinbeneflciating those rock the grade of concentrate obtained is toonon-metallic ores which are amenable to flotalimited. On the other hand,a fatty acid alone did tion with anionic promoters of the fatty-acid notprove successfulin any ordinary procedure. soap type and to a method ofusing such re- Saponifled fatty-acidsinsome cases proved someagents.what more effective. Even with soaps however,

Beneficiation of various ores by froth flotation, consumption was highand the metallurgical retaking advantage of the selective afilnity ofvarisuits were generally poor. In compromising beous materials forparticular mineral constituents tween these factors, it came to bconsidered nechas come to be common practice. One of the most essary touse with the fatty acid both a saponifycommon procedures in that fieldis the use of a ing agent, the caustic soda; and a modifying fatty acid,or a soap thereof, as the selective agent, the oil.- This 'was thoughtnecessary in reagent. An excellent illustration of such usage order toinsure eflicient distribution and lower th is in the beneficiation ofphosphate rock, particufatty-acid consumption,

larly the treatment of rock from the Florida Peb- Having come to be moreor less standardized ble Phosphate District. Since most of theprobpractice, the art began to seek more economical lems to be overcomeare met in this operation, reagents. Principally this led to variationsin the the present invention, although not necessarily an nature andamount of the fatty-acid used. Some so limited, will be principallyillustrated with rela appear to have greater selectivity, others givetion thereto. This is a P rtic l rly 8 0 i lll equivalent results onlywhen used in. excessive tration since it represents one of the bestexquantity, Talloel, a, mixture of fatty and resin amples oflarge-volume, low-cost operation in acids, was generally found the mosteconomical which even small savings per unit become of ofthe fatty-acidreagents. In some cases, for

marked commercial importance. example in phosphate flotation, it alsowas found For many years, in this field, the practice has to be one ofthe most emcient. Likeother fattybeen standardized on a flotation agentcombinaacid reagents, however, for best results it was tion comprisingan alkali, such as caustic soda; generally considered desirable to usetherewith a fatty acid, such as oleic acid or the like; and an 80 asaponifying agent and, in phosphate flotation, unsaponifiable oil suchas kerosene or fuel oil. a non-saponifiable oil. The actual process ofusing these agents may be V Where talloel or a talloel soap can besuccessvaried. For example, the reagents may be prefully used, a naturalinclination is to attempt to combined before being fed to a pulp of theore or make use of the less expensive, crude, black-liquor they may befed separately in various sequences 35' soap. In addition to its generalavailability and or combinations. They may be added to the ore low cost,such material looks particularly attracpulp in a preconditioningoperation or during flotive because it is in soap form. It would appeartation. Supplementary conditioning, dispersing therefrom thatconsiderable economy in alkali or depressing agents are also sometimesused. Reconsumption might be effected by its use. gardless of procedure,however, the reagent com- 0 Unfortunately, a direct substitution ofblack bination normally is comprised of one represenliquor soap for afatty acid or the talloel of the tative of each of these three classesof materials. prior art, or for soaps of these materials, does not Anumber of reasons contributed to the develproduce satisfactory results.Such substitution, opment of this practice. A straight oil flotation,particularly in phosphate flotation, does not give useful insome fields,suffered from fairly high reresults which are of suflicient utility tobe commercially acceptable. There remained, therefore,

the desirability of using black liquor soap as a substitute forflotation reagent materials in commen use, but no practical method ofsatisfying the demand.

It is, therefore, the principal object of the present invention todevelop a process in the practice of which black liquor soap can beutilized to produce an effective and acceptable beneficiation ofnon-metallic ores. In particular, it is one of the principal objects ofthe invention to devise a process whereby black liquor soap can beeffectively used to reduce the acid-insoluble content of phosphateconcentrates.

Surprisingly, the desired object of the invention can be easily andsimply accomplished by the exercise of a practice which is exactlycontrary to that taught bythe prior art. According to the presentinvention, it has been found that the desirable results areaccomplished, not by using the black liquor soap in conjunction with analkali, but by carrying out the operation in a circuit to which a strongacid has been added. This is particularly surprising since, as notedabove, effective results in an anionic flotation of ores such as pebblephosphate were previously considered possible only on the presence ofexcess alkali.

On the contrary, in the practice of the present invention, the optimumresults in phosphate flotation are obtained when the tailing water has apH less than 6.9.

In this respect it should be noted that an ore pulp frequently mayappear to have an-alkaline pH whereas the tailing watermay be distinctlyacid. Whether this is dueto the alkaline reaction of black liquor soapor to some pulp pretreatment or to the presence of other reagents,however, may

be uncertain. An instance of this may be found for example in phosphatefloatation. The pulp even after being conditioned "with the otherreagent or reagents in the presence of the acid may have an apparent pHof 7.0 to 7.5, yet the pH of the rougher tailing water willbe only6.5-6.7. Where there is a discrepancy between the apparent pH of the orepulp and that of the tailing water, the latter shouldv be the chosencontrol since the removal of much or all of the solids content therefromenables a more accurate reading to be taken.

It is for asimilar reason that the beneficial effect of adding extraacid in the present process may not always Foe immediately observable.For example, a particular mill may be using process water whichnaturally, or because of prior use, has an inherent pH less than 6.9. Insuch cases addition of more acid, to a phosphate flotation for example,will not produce a particularly marked improvement in grade over thatobtained when using black liquor soap'without added acid. Nevertheless,the improvement over the prior practice, in which excess alkali wouldhave been added without realizing the advantage in the acid water, isvery real.

The present invention is in no way concerned with the practice ofrefining talloel in which crude black liquor soap is acidified to freethe talloel. The amount of acid used in the process of the presentinvention is but a fraction of that needed to neutralize the totalalkali content of the black liquor soap. In fact, the presence of freeacid in the flotation circuit of the present invention is possible onlybecause neutralization of the black liquor soap is very slow. Flotationis completed after the pH change takes place but before the acid isexhausted: In addition, if a large excess of acid, i. e., sumcient toliberate the talloel content, is used, the catalytic effect of the acidon selectivity during flotation is not obtained. The benefit of the freeacid on the selectivity of the black liquor soap is not observed at a pHless The distinguishing characteristics of the present inventiontherefore may be summarized as:

(1) the benefication of non-metallic ores, particularly phosphate orescontaining an excessive content of silica-bearing gangue; (2) byproducing a froth concentrate high in mineral values; (3) in an anionicflotation; (4) using black liquor soap as the collector; (5) in thepresence of suflicient acid to activate the selective tendency of thecollector, but insufficient to neutralize the black liquor soap;normally enough to produce a tailing water-pH of from about 4.0-6.7; and(6) completing the flotation before the acid is consumed in neutralizingthe alkali content of the black liquor soap.

I The present invention will be more fully illustrated in connectionwith the following examples which are meant to be illustrative only andnot by way of limitation. All parts are by weight unless otherwisenoted. In tabulating the results, the following abbreviations are used:B. P. L.- bone phosphate of lime (Caa(P0i)2); B. L. S. or B. L.Soap-black liquor soap; Insolacid insoluble gangue.

Example 1 A sample of Florida pebble phosphate ore, assaying about 43.4%B. P. L. and 43.5% Insol, was prepared for flotation by reducing thesize sufliciently for flotation feed; pulping with water, to about 22%solids; polishing in a Fagergren flotation machine with the air shut offfor 6 minutes; and completely desliming by conventional hydraulicprocedures. This sample was then divided into a number of portions whichwere separately conditioned at about 70% solids with various amounts ofblack liquor soap, diluted to about 20% solids and floated in Fagergrenflotation machines under standard conditions, including a rougher floatfollowed by 3 cleaner floats. The procedural steps and metallurgicalresults appear in the following table. The first test is a blank with noacid, followed by three tests in which the acid was added to theflotation cell and then by three tests in which varying amounts of acidwere added during conditioning.

Results Reagents Lbs. on Cleaned Concentrate Added to Conditioning 1 pHTest No. R. Tail Assays Dist. I Water 9;, Wt B. L. s. also Insol B. r.L.. Insol B. r. L.

' Added to flotation cell.

grades are obtained with amounts above /6 1b.,

and recovery remains good until lb. is reached, at which point therecovery begins to drop.

froth flotation u'slng 2 .0 lbs/ton of black liquor inthe followingTable II.

. Table II A Assay-spodumene Content Acid (Lba/Ton) Taillnl;

' .Water pH Feed Sp. Ro. Tail Cl. Tall 01. Cone.

9;, Sp. Dist. Sp. Dist. sp. not. R0 01.

2 6.16 5 1Z2; 19 92.6 1.1 1.1 2 20.33 10 1 121 14 65.5 0.5 6.7 6.9 13.63 10 5.95 on 00.4 .25 0.25 6.8 6.2

Nora: Sp.=Spodumen'e. dist.=% Distribution. While the present inventionis primarily con- Example 3 cerned with the use of acid and black liquorsoap in the beneflciation of phosphate ores, the invention is notnecessarily so-limited. The mineral values of many non-metallic ores arecommonly concentrated by an anionic flotation using fatty acid soapreagents. In general, these types of operations may be adapted to thesubstitution of black liquor soap for the more expensive reagents incommon use if the acid treatment of the present invention is joinedtherewith. In order to demon- A low grade fluorspar ore was treated bygrinding for 15 minutes at about 67% solids in a rod mill after whichthe pulp was diluted to about 4 22% solids and conditioned for 5 minuteswith strate this feature, the following examples are given for purposesof illustration.

Example 2 1 lb./ton of sodium silicate and 1 lb./ton of quebracho. Whereacid was used in the rougher float it was added during this conditioningoperation. The conditioned pulp was transferred to a flotation machineand given a 6 minute rougher float in which the black liquor soap wasstage-added. The rougher, concentrate in the second and third tests wasconditioned for 1 minute withthe sulfuric acid and given a 2 minutecleaner flotation. The cleaner concentrate was conditioned for 1 minutewith additional black liquor soap and in i the second and third testswith sulfuric acid. and

given a 2 minute cleaner flotation. The reagents used and representativemetallurgical results are shown in the following Table 111. It will benoted that the use of acid throughout the process results in anextremely high grade concentrate in a field in which grade is primarilyimportant.

Table III Concentrate Rte Feed AS88178 Assays R0. Float 01. Float Bocl.Float Wt.

9506!: 930600; %CBF: %Ca00i B. L. S. H1804 B. L. 8. H1804 B. L. S. H1804I claim:

1.111 the beneflclation of non-metallic ores by froth flotation, usingat least one rougher and one cleaner stage, to recover the mineralvalues in a high grade concentrate, the improvement which comprisessubjecting an aqueous pulp of the .ore to iroth flotation at least therougher" float being carried out in the presence of an effective amountof black liquor soap as the principal collector and a suflicient amountof free strong acid to produce a pH of from not more than 6.7 or lessthan about 4.0 in the tailing water, but insufllcient to neutralizeappreciable amounts of-the alkali content of the black liquor soapduring the period of operation. i

2. In the beneflciation of phosphate ores to recover the mineral valuesin a high grade concentrate, the. improvement which comprises subjectin:an aqueous pulp oi the ore to froth flotation in the presence of aneflective amount of black liquor-soap as the principal collector and a sm- 8 clent amount of free strong acid to produce a pH of not more than6.7 or less than about 4.0 in the tailing water but insufliclent toneutralize appreciable amounts of the alkali content of the black liquorsoap during the period of operation.

ELMER WILLIAM GIESEKE.

REFERENCES CITED The following references are of record in the flle ofthis patent:

UNITED s'ra'ms PATENTS OTHER REFERENCES Soap Flotation by Coghill inMilling Methods, 1934, pa es 452, 462, 463, 464,

